Adsorption Behaviour of Modified Organobentonite with Dithizone for Hg(II) in Water and Its Application for Concentration and Separation of Hg(II) in Surface Water

Abstract

In this paper, the adsorption behaviour of modified organobentonite with dithizone (D-O-bentonite) for mercury(II) in water was investigated. Optimal experimental conditions for the adsorption of the mercury, including pH, contact time, eluent concentration and volume and co-existing ions have been studied. Moreover, the thermodynamics and kinetics of the adsorption were completely investigated. The result showed that the Hg(II) could be adsorbed on the D-O-bentonite. The adsorbed quantity was affected by the pH value of medium and contact time. The isothermal data was described by the Langmuir equation. The dynamic data followed the pseudo-second-order kinetic model well. The enthalpy change (DH) of the adsorption process was 14.20 kJ/mol. Gibbs free energy changes (DG) were negative and entropy changes (DS) were positive. The activation energy (E_a) was 14.06 kJ/mol for the adsorption. The mercury adsorbed on the D-O-bentonite could be completely eluated by using 3 mol/L HCl. The adsorption agent has been applied to the pre-concentration/ separation of Hg(II) in surface water samples with satisfied results.